Application of Hierarchical Two-Level Spectral Preconditioning Method for Electromagnetic Scattering from the Rough Surface

Table 1

Construction time and solution time (in seconds) for the orthogonal plane scatterer.

Basis functions	Mesh sizes	Unknowns	Solution methods	Construction time	Iteration step	Solution time	Total time
2-order	0.3𝜆	11,502	GMRES	—	439	552	552
			FGMRES	—	45	65	65
			Two-level	69	17	22	91
3-order	0.5𝜆	9,072	GMRES	—	958	783	783
			FGMRES	—	73	103	103
			Two-level	32	18	15	47